Electrode for electric furnaces



Patented Aug. 25, 1931 UNITED STATES PATENT OFFICE PAUL LOUIS JOSEPH MIGUE'QI, or ST.-JULIEN mi Macrame, FRANCE, ASSIGNOR 'ro SOCIETE ELECTRQMETALLURGIQUE DE MQNTRICHEB, OF ST.J'ULIEN DE MAU- I RIENNE, sAvorE, FRANCE ELECTRODE FOR ELECTRIC FURNACES No Drawing. Application filed June 28, 1928, Serial No. 287,896, and in France March 31, 1928.

This invention relates to improvements in electrodes for electric furnaces.

Heretofore electrodes have been made in cylindrical sections adapted to have the end of onesection secured to the end of another section to form what is known as a contmubaked or coked prior to placing the electrode into operation andthe subsequent sections.

' are usually added to the electrode with the .materials are then baked in heat of the furnace while it IS 1n operat1on.'

filling material 'in the raw state and these It is known that such binding materials give ofi a quantity of Volatile matter while they are being converted into a solid state by the application of heat, and that an increase in the quantity and in the rate of evolution of the gases from the filling material causes an increase in the porosity and a decrease in the durableness of the electrode.

Therefore one of the objects of my invention is to perfect a method of baking an electrode Without generating an excessive quantity or rate of evolution of gas.

1 Another object of my invention is to produce a compact, durable electrode.

The invention disclosed herein is an improvement of the electrode described in my concurrent application Serial No. 242,224 filed December 23, 1927.

According to my invention the electrode comprises a hollow conductive shell into which a carbonaceous filler is packed. The filling material comprises finely divided coal or a mixture of finely divided coal and an inert material which contains little or no volatile matter, such as coke, furnace dust or primary materials to be treated such as those described in U.- S. Patent No. 1,7 07,406. The filling material should have in itself coking properties necessary to produce a solid lace from the compact mass at temperatures below 1000 C. without the evolution of great quantities of volatile matter. Therefore I desire to select a coal of a bituminous nature for at least one ingredient of my filling material and I desire to exclude such binding materials as pitch, resin or tar.

The coking factor of the filling material may be controlled by varying the ratio of the quantity of the coal to the quantity of inert materials, that is materials which evolve substantially no gas when subjected to heating.

As a further precaution to eliminate the evolution ofgases during the baking of the electrode, itis desirable that the chosen filling material be completely desiccated before it is placed in the electrode shell. This may be efiected'by commencing and then stopping distillation at the proper point. I

Also the proportion of ash in the filling material should be, as far as possible, below 6% in normal electro thermal cases and below 1% in the case of electrolysis such as that of aluminum.

The grade of coke obtained in the coked portion of the electrode is controlled not only by the proper selection of the primary filling materials for the electrode but it is also controlled by the proper regulation of the temperature to which the materials are. subjected at the various stages of their conversion into the final coked product.

The proper regulation of the temperature is automatically controlled due to the fact that the heat required to convert the filling material into coke is derived almost exclusively from .the heat liberated at'the lower end of the electrode and this heat is gradually conducted upwards through the filling material and the electrode shell. Substantially no direct electro thermal heat is produced in the raw filling material by the passage of current therethrough because the material is converted into a'semi-coke in the mid upper half of the electrode where the temperature is maintained at between 500 C. and 600 0., and the coking of the filling material is gradually completed as the lower end of the electrode is consumed and the electrode is fed into the furnace.

My invention is capable of being modified and adapted for several uses. For example,- an electrode may be formed by substituting the electrode filling material described herein for that used to fill the hollow cylindrical carbon shell described in U. S. Patent No. 1,707,406. In such a case where the filling material is composed wholl of carbonaceous materials it will serve principally to protect the inner portion of the shell from the furnace heat and to prevent the escape of gases through the electrode shell, and Where the carbonaceous filling materials are mixed with materials to be treated when the filling materials act also as a conveyor of these materials to the furnace.

Due to the solidity of the packed raw filling materials used in my electrode it may be provided with a shell of sheet metal and it will not be subject to be deformed by the pressure of the electrode holder as would be the case if the filling materials contained such deformable binding materials as pitch,

resin or tar. Due to the solidity of the electrode it is not liable to slip in the electrode holder. The electrode is therefore very deendable and it is very suitable for use in Both open and closed type furnaces.

' As the filling material used in my electrode cokes at a relatively low temperature the electrode may be used in low' temperature furnaces as well as in furnaces which operate with temperatures above 1000 C.

Among other uses of my electrode it may be used to superheat steam where the steam is superheated to the neighborhood of 600 C.

In initially placing the electrode into operation it is advisable, sable, to previously bake the bottom end section at a high temperature. The subsequent sections may be baked after they are assembled in the electrode and during the operation of the electrode. It may be found advantageous to compact the filling materials into the shell before they are assembled on the electrode in operation instead of packing the materials into the shell after it has been secured to the lower sections then in operation. a

I claim: 1. An electrode for electric furnaces said" electrode having a conductive shell of preformed material, a filler of unbounded earbonaceous material in the upper end of said shell and a filler, of bonded carbonaceous material in the bottom end of said shell.

2. An electrode for electric furnaces said electrode having a conductive shell of prein the upper end of said shell and a filler of coke in the bottom end of said shell.

formed material, afiller of unbounded coal 3. An electrode for electric furnaces said and an inert material in the upper end of said shell and a filler of coke in the bottom end of said shell.

4. The method of forming an electric furnace electrode comprising packing unbonded carbonaceous materials into a hollow conductive case; passing current through the electrode and converting the materials at a low temperature into a compact mass with the heat derived from the operation of the furnace.

'5. The method of forming an electric furnace electrode comprising packing unbonded coal into a hollow conductive case; passing current through the electrode; and coking the materials at a low temperature with the heat derived from the operation of the furnace.

In witness whereof I affix my signature.

PAUL LOUIS JOSEPH MIGUET.

but not indispen- 

